Please add a public description of the issue, thanks!

Description of problem:
Setting features by using the "volume option set" cmd is not always consistent.
In some cases it will take any given input while in other cases boolean values are to be accepted only.

example 1: gluster volume set <vol> nfs.disable fun
(Will report back: "fun" is not a valid boolean value)

example 2: gluster volume set <vol> features.uss type_whatever
(will report back: "volume set: success")

If you now ask volume status on <vol>, it will actually show:
"deatures.uss: type_whatever"


Version-Release number of selected component (if applicable):
Mainline

How reproducible:
Every time

Steps to Reproduce:
1.Install RHS
2.Create volume
3.Set volume option using any fictional option
4.System will accept fake option without any rejection

Actual results:
Accepts any given option (whilst using i.e. features.uss option, among others)
and will show the fake option while querying volume status

Expected results:
Denial of any other option then on|off or enable|disable as boolean values

Additional info:
This is true for several options, where others behave like expected.
Notices this behavior for the following options while testing;

- features.uss
- rpc.auth allow

pre-release version is ambiguous and about to be removed as a choice.

If you believe this is still a bug, please change the status back to NEW and choose the appropriate, applicable version for it.